[otrs] How can I select more than 28 tickets for bulk action?

Hi all! I have been reading the whole OTRS manual, and I found some tips. For example in my queue view now I can view more than 25 tickets (actually I see 100 tickets). However, I'm not able to select the whole tickets for bulk action; When I try it, I only get 28 selected tickets in the bulk action screen, and not the hundred I tried. Does anyone knows wich filed must I modify in order to select all available tickets for bulk action?, and then in the bulk action screen be able to see all these previous selected tickets ready for a bulk action? Thank you and best regards! -- David